<?php
/**
 * Created by PhpStorm.
 * User: zhangrongxiang
 * Date: 2018/2/12
 * Time: 下午7:43
 */

$arr = [
	"C"      => "I am the GOD",
	"PHP"    => "PHP is the best language int the world",
	"Python" => "Life is short, I use Python",
	"Java"   => "Write once, run anywhere",
	"Go"     => "better C",
	"ZING"   => null
];
if ( array_key_exists( 'C', $arr ) ) {
	echo 'C exists' . PHP_EOL;
}

if ( array_key_exists( 'ZING', $arr ) ) {
	echo 'ZING exists' . PHP_EOL;
}
if ( ! isset( $arr['ZING'] ) ) {//true
	echo 'ZING not exists' . PHP_EOL;//
}